Browsing by Subject "Paleontology--Pleistocene"
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Item The bench deposits at Berger Bluff : Early Holocene-Late Pleistocene depositional and climatic history(2006-05) Brown, Kenneth M.; Hester, Thomas R.; Wilson, Samuel Meredith, 1957-This study reports original field and laboratory studies on paleoenvironmental aspects of the Berger Bluff archeological site (Goliad County, Texas). It uses data from geoarcheology (stratigraphy, grain-size analysis, magnetic susceptibility and sediment thin sections) and several different biotic indicators (chiefly diatoms, snails, freshwater mussels, and vertebrates) of environmental change to reconstruct past environments of the site and upstream drainage, and relate these events to regional and global paleoenvironment. Berger Bluff is a sandy bluff about 9 m high on the west, or Goliad County side of Coleto Creek, west of Victoria. The bluff (41 GD 30A) records continuous deposition of sediments by Coleto Creek from the Late Pleistocene until the Late Holocene. The lowest 2.45 m of deposits form a prominent erosional bench from floodplain sediments cemented by phreatic carbonate, probably representing the fossilized damp margin of a spring or seep area, although no actual spring conduit was visible. Based on a series of radiocarbon assays, they are estimated to date from about 8500-11,000 radiocarbon years before present (or 9500-13,000 calendar years), but there are no assays from the upper or lower part of the bench, and there are a number of inversions among the assays. This corresponds to the Younger Dryas, Preboreal, and part of the Boreal period in the climatic chronology, and the Folsom and Late Paleoindian periods in the cultural chronology, although none of the artifacts from the bench are time-diagnostic. The bench consists of fine-grained overbank deposits (cyclically bedded sandy and muddy units) formed by vertical accretion near the south valley wall. Sedimentary evidence suggests the creek was probably narrower, deeper, more sinuous, and carried a much greater suspended load during the Younger Dryas/Early Holocene compared to today. Rainfall was probably less seasonally concentrated, discharge less flashy, and flood duration longer. The floodplain was probably wider, flatter, less drought-prone, and (based on evidence from snails and vertebrates) covered with a heavier, more continuous deciduous tree canopy than today. These conditions probably lasted some 1500 years into the Holocene, until regional drying and flash flooding stripped the wet riparian habitat out of Coleto Creek and other small tributaries on the Gulf Coastal Plain.Item Late Pleistocene and Holocene faunal and environmental changes at Hall's Cave, Kerr County, Texas(1993-05) Toomey, Rickard Stanley, 1963-; Lundelius, Ernest L., 1927-Hall's Cave contains 3.7 meters of well-stratified, bone-bearing, elastic sediments. Eleven radiocarbon determinations provide good temporal control and indicate that deposition occurred fairly continuously over least the past 15,000 years. These sediments contain abundant, well-preserved vertebrate remains that reflect the changing central Texas faunas through the latest Pleistocene and Holocene. Hall's Cave contains the remains of at least 62 species of mammals and at least 48 species of non-mammals. The fauna includes at least 12 extinct (one turtle, 3 birds, and 8 mammals) and 22 extralimital taxa. The paleoenvironmental study of the fauna includes the analysis of climatic tolerance of important taxa based on their geographic ranges. During the Last Glacial Maximum, the central Texas climate was cooler and moister than modern. Mean annual temperature was probably 5°C or more cooler, and summer temperatures were at least 2°C cooler. Effective moisture was higher in all seasons and precipitation was probably higher in the summer. The eastern and central Edwards Plateau was covered with a deep red soil that supported a diverse grassland community. Between 14,500 and 12,500 RCYBP rapid warming and possibly drying occurred. This resulted in the extirpation of several cool and/or mesic adapted species. By 12,500 the temperature of the Edwards Plateau may have been close to modern conditions. The drying was part of gradual trend of decreasing moisture that peaked at approximately 3500 RCYBP. Several more mesic intervals, approximately 10,400 to 9000 RCYBP and approximately 2500 to 1000 RCYBP, interrupted the general drying trend. After 1000 RCYBP drying conditions resumed. Gradual down-wasting of the soils accompanied the drying and resulted in decreasing soil depths. This soil loss led to the extirpation of numerous burrowing taxa. Throughout the interval the western Kerr County area was covered with an open vegetation, probably a grassland or open savanna.Item New perspectives on Pleistocene biochronology and biotic change in the east-central Great Basin: an examination of the vertebrate fauna from Cathedral Cave, Nevada(2007-12) Jass, Christopher Nathan, 1970-; Bell, Christopher J., 1966-The interaction between climate, environments, and mammalian faunas during the late Pleistocene-Holocene has been studied intently over the last several decades. Cave deposits play an important role in our understanding of these complex interactions, but they are especially significant for our understanding of the faunal history of the Great Basin. In order to develop a deeper time perspective on mammalian faunal change, I began a project that integrated several elements necessary for identifying and interpreting biotic change in the Great Basin of the western United States. These elements included development of a framework for understanding the importance of cave deposits for the paleontological record, collection of a mammalian fauna that pre-dates the terminal Pleistocene, identification of that fauna in the midst of shifting taxonomic paradigms, and evaluation of the fauna in the context of previous regional biogeographic models. I utilized data from the FAUNMAP database to evaluate the significance of the contribution that cave deposits make to the Pleistocene mammal record. Caves do provide unique faunal data in addition to contributing a high percentage of the individual species records for late Pleistocene mammals. Fieldwork was conducted at Cathedral Cave, NV, in order to assess a fauna that was thought to predate the late Pleistocene-Holocene transition. In excess of 30,000 identifiable fossils were recovered in an excavation area that was roughly 1.5 x 2 x 0.7 m. Prior to fieldwork in 2003, age estimates for the fauna were between 750 ka to 850 ka. New chronologic analyses suggest a more recent age (≤146.02±2.584 ka to 151.2±4.4 ka) that extends the known chronologic distributions of several taxa and alters previously established biochronologic frameworks for the Pleistocene. This work also calls into question previous age assignments for portions of Smith Creek Cave. Individual faunal identifications were made using a conservative data-reliant approach in order to minimize geographic assumptions and render an independent data set useful for broad biogeographic analyses. Although the faunal data presented here do not explicitly support or refute regional biogeographic models, they do indicate that patterns of faunal change can be found even when species-level identification are not achieved.